[Elecraft] FSK power

[Richard Ferch]

The specifications for the transmitter in the Owner's Manual say 100% 10 
min 100W key-down at 25 C ambient, so RTTY at 100 watts is within spec 
even for extended transmissions, and an RTTY contest with its short 
transmissions should be no problem at all at 100 watts.

You can monitor the temperature of the finals by tapping the DISP key 
and rotating the VFO B knob until you see PA xxC (where xx is the 
current temperature). I believe there is a protective thermal shut-down 
somewhere up around 80C, but I doubt whether you will come anywhere near 
that. Mine gets into the mid-50s near the end of long transmissions 
during digital mode ragchews, but it doesn't get that hot during 
contests. The ambient temperature has a significant influence, too.

If you do monitor the PA temperature, don't be surprised if you observe 
temperature readings that are slightly higher during receive than during 
transmit periods. The voltage drop in the power cable at the high 
transmit current draw results in lower voltage at the rig, which in turn 
causes the temperature indication (not the actual temperature) to drop 
slightly. In digital modes I often observe the fans speeding up in 
receive and slowing down in transmit when the PA temperature reading 
happens to be close to the threshold for a fan speed change. I found 
this disconcerting at first, until I realized what was happening!

73,
Rich VE3KI


NR4C wrote:

> Now, one more. How much power can I safely use with FSK? I have made
> several contacts so far at about 50 watts. Can I use more? there is a
> RTTY contest this weekend, and I don't want to damage the radio, but
> don't want to start off with a weak signal if I can do better.